1. Field of the Invention
This invention relates to an electronic flash device having light distribution control means.
2. Related Background Art
As shown in FIG. 5 of the accompanying drawings, there has been an electronic flash device 106 capable of selecting the postures of horizontal position a, c and a vertical position b by the rotating mechanism of a leg 112 when the flash device is mounted on a camera 100. The reason why such a mechanism is adopted is that it is desired to move the position of the light emitting portion 106a of the electronic flash device 106 relative to the optical axis of a photo-taking lens 107 for the purpose of controlling the shadow of the background of an object in photographing using the electronic flash device. A system in which a rotating mechanism is provided on the leg 112 and the entire electronic flash device 106 is rotated is simple in structure and therefore has merits of compactness and great durability.
Now, as regards the light distribution of an electronic flash device, in a 35 mm single-lens reflex camera as shown in FIG. 5, it is preferable that in accordance with the angle of view of the camera, light distribution be wide in the horizontal direction and light distribution be stopped down in the vertical direction. By doing so, the object field can be illuminated more efficiently than by light distribution called non-directional or circular light distribution and the guide number is increased and the photographable distance also is increased. In FIG. 5, the electronic flash device 106 has a light distribution stopped down in the horizontal direction in the horizontal position a.
When in actually using such an electronic flash device 106, the electronic flash device 106 is brought into the horizontal position b, the angle of view of the photo-taking lens 107 cannot sometimes be covered because the light distribution in the horizontal direction is narrow. For example, let it be assumed that a photo-taking lens of focal length 35 mm is used in the camera 100 and the electronic flash device 106 has a light distribution covering the photo-taking lens of focal length 35 mm at the horizontal position a, c. At this time, specifically, the light distribution in the vertical direction is 45.degree. and the light distribution in the horizontal direction is 60.degree.. When the electronic flash device 106 is brought into the vertical position b, the vertical direction and the horizontal direction change places with each other and therefore, the angle of view in the vertical direction can be covered, but the angle of view in the horizontal direction cannot be covered. So, there has heretofore been an inconvenience that the electronic flash device 106 is used with a wide panel mounted thereon only when the flash device is brought into the vertical position, or with the wide panel always mounted on the electronic flash device to avoid cumbersomeness and with the guide number reduced.
Also, this problem is attributable to the fact that the light emitting portion 106a rotates about the rotating mechanism of the leg 112, and to prevent the light emitting portion 106a from rotating relative to the angle of view of the camera 100, the downsizing of the electronic flash device is precluded only in the portion of that rotating mechanism. Also, if the light distribution characteristic is made non-directional, the influence of rotation will be eliminated, but the guide number will be reduced as previously described.